Intel Core i7-7740X Kaby Lake-X Review

Last month, Intel's Skylake-X processors debuted at lower price points than we might have expected, given the company's previous high-end desktop CPU launches. The new chips also feature hefty core counts, higher Turbo Boost frequencies, a revamped implementation of Turbo Boost Max 3.0, a realigned cache hierarchy, and a new mesh topology. If you haven't read our review yet, check out Intel Core i9-7900X Review: Meet Skylake-X.

Interestingly, the seven new Skylake-X models are accompanied by two quad-core Kaby Lake-X SKUs. In the past, Intel's entire HEDT portfolio lagged at least a generation behind the mainstream offerings. But Kaby Lake-X puts Intel's most modern architecture in the LGA 2066 interface.

It's only unfortunate that this attempt at rejuvenating the high-end desktop leads to a confusing mix of features on the X299 platform, many of which Kaby Lake-X simply does not support. Fewer PCIe lanes and a dual-channel memory controller are an obvious mismatch with expensive LGA 2066-equipped motherboards, and that's bound to create a dubious value proposition.

Kaby Lake-X Becomes Core i7-7740X

There are slight differences between the familiar Core i7-7700K (Kaby Lake-S), which drops into LGA 1151, and the new Core i7-7740X (Kaby Lake-X) designed to complement the X299 chipset.

Intel increases the -7740X's base frequency by 100 MHz to 4.3 GHz, but leaves the 4.5 GHz Turbo Boost clock rate and 8MB of last-level cache unchanged. The chip's TDP does jump from 91W to 112W, but that's not from any gain in host processing resources: we're still looking at four IA cores and the GT2 configuration of Intel's graphics engine with 24 EUs.

Although the HD Graphics 630 hardware is physically present, Intel fuses it off. This eliminates many of the multimedia features that benefit the mainstream market. Perhaps they won't be as missed in the enthusiast space, though. You do lose Quick Sync, which is useful for accelerating streaming, along with HEVC encode/decode and PlayReady 3.0 "enhanced content protection" support. On the other hand, X299 enables a more robust power delivery system, so cutting out HD Graphics could prove beneficial to our overclocking efforts. After all, the disabled hardware serves as dark silicon, absorbing waste heat from the active on-die components.

Purportedly, a larger heat spreader and package add to Core i7-7740X's capacity for dissipating thermal energy. Since CPUs vary in their ability to sustain Turbo Boost clock rates depending on their thermal headroom, the -7740X might also enjoy a larger window of higher frequencies, improving performance in our benchmarks compared to Core i7-7700K. It's too bad that Kaby Lake-X uses the same thermal interface material as the mainstream models, instead of indium solder.

The -7740X shares a 16-lane PCIe 3.0 controller with Intel's Core i7-7700K, and we'll dive into that liability shortly. DDR4 memory support is officially extended to 2666 MT/s, at least. That's a small improvement over the S-series’ sanctioned 2400 MT/s ceiling. The speed-up isn't related to any architectural enhancement. Rather, Intel tells us it adjusted the dual-channel controller's spec based on “significantly more test and manufacturing data” that suggested an increase was safe.

Surprisingly, the Core i7-7740X bears the same price as Core i7-7700K. So, in short, it looks like Intel took an existing CPU, tweaked a couple of knobs, and adapted it for the larger LGA 2066 interface with different packaging. The end product does overclock a little better than Core i7-7700K, we've noticed.

The Motherboard Land Of Confusion

The new X299 chipset, code-named Basin Falls, goes hand-in-hand with the LGA 2066 interface. Intel moved away from its normal tactic of recycling an enterprise-oriented platform controller hub and instead built X299 to be a beefed-up version of the Z270 chipset.

The Core i7-7740X's 16 lanes of PCIe 3.0 and two memory channels present issues, though. X299 must naturally accommodate Core i9-7900X with its 44 lanes of PCIe 3.0 and quad-channel DDR4 controller, but has to be flexible enough to take the Core i7-7740X, too. That means the lower-end CPU limits you to using four of the eight DIMM slots found on corresponding motherboards. Moreover, some PCIe or M.2 slots might not work when you drop in a -7740X.

The processor still features a DMI 3.0 link to X299, which is similar to a four-lane PCIe 3.0. The chipset supports a hefty 30 HSIO (High Speed I/O) lane allotment that vendors can carve up for expanded functionality. X99 did not support HSIO lanes, so that's a significant addition.

With Core i7-7740X, there isn't a difference between the features you can use on the X299 platform compared to what is already available from the Z270 chipset. X299-based motherboards are undoubtedly high-end parts, and they bear the price premium (~$150) to prove it. That means you're paying for features that you cannot use, which is never a positive selling point.

To reduce costs, Intel tells us that motherboard partners can build Kaby Lake-X-specific platforms with only four DIMM slots to accommodate the new processors. We haven't seen any, though, and we haven't had a single vendor tell us they're working on one.

To make matters worse, none of Skylake-X’s unique features are available from Core i7-7740X, including Turbo Boost Max 3.0, AVX-512 support, the integrated vROC (Virtual RAID on CPU) controller, or Intel's mesh/cache adjustments.

All of these factors combine to create a questionable addition to Intel's high-end desktop portfolio. The company tells us that Kaby Lake-X offers a cheaper way into X299 with an upgrade path for later. We don't think many enthusiasts are interested in paying more now for the potential to upgrade later, though. Can Intel prove us wrong?

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33 comments
    Your comment
  • AgentLozen
    I'm glad that the option for Kaby Lake is available on the x299 chipset. In practice it seems impractical. This article shows you have to pay a lot more for slightly higher overclocking potential.

    I'm curious what Intel's plans are for next year regarding their high end desktop chips. They've already used the Kaby Lake X name for this generation. Should we expect Kaby Lake X 8900X?
    0
  • Kaz_2_
    Intel high power consumption is not great in thr long run. You want the best for your investment
    0
  • TJ Hooker
    Quote:
    The curve below shows clearly that waste heat isn't dissipated quickly enough. Just as we did in our AMD Ryzen and Intel Core i9 launch articles, we used a very thin copper plate to measure the heat spreader's temperatures as well.

    Why aren't there any numbers/divisions on the horizontal axis? Also, you say you did the same thing for the Ryzen reviews but I didn't see a similar graph in those articles (might just be blind though).
    0
  • keith12
    in the HPC graph, you have two 'Ryzen 7 1600x' s.....
    0
  • keith12
    power consumption gaming loop - I5 7600x?
    0
  • the nerd 389
    How does the thermal performance of this chip compare to the 7700k? Specifically, does the larger surface area of the heat spreader give you a meaningful increase in thermal conductivity between the die and the heatsink?
    1
  • rantoc
    Dang intel seem to be doing yet another stupid move with X299 beside rushing it out the door making the AMD's pretty brand new architecture/platform appear mature in comparison. As for this move - What's the incentive to pay premium for the X299 when getting a chip like this that won't even utilize it fully? The 7700k and platform are equal in performance in most tests and far cheaper...

    With the poor thermal transfer between the core and heat-spreader the retail chips won't likely even overclock well either. Never cared about the cherry picked "reviews" chips at all when it comes to overclocking as they very rarely represent the retail chips.
    4
  • rantoc
    What's the incentive to buy an expensive motherboard and yet get near zero of it's true potential with this cpu? That's paying for a lot of real estate that can't be used at all and on top of that the same poor thermal transfer between the core and heat-spreader meaning a good stable oc is harder to obtain and far less likely to happen on the retail IE non-review cherry picked ones.

    I think intel shoot themselves in the foot by scaling this one down to much and then couple it with an overpriced platform for what you get out of it, x299 will be good no doubt but only with the right chips and only when the rushed out of door bugs been fixed.
    3
  • Anonymous
    This is awesome setup because you can buy x299 motherboard for $219 dollars already which gives you amazing room for later upgrade and this CPU can run 5.0Ghz easily producing very little heat. People at Toms Hardware completely missed the point. I'd rather get $219 x299 motherboard than outdated Z270 for $160.
    -8
  • Anonymous
    And as for heat...i think heat talk i have been reading lately is just BS.
    -2
  • AgentLozen
    Quote:

    This is awesome setup because you can buy x299 motherboard for $219 dollars already which gives you amazing room for later upgrade and this CPU can run 5.0Ghz easily producing very little heat. People at Toms Hardware completely missed the point. I'd rather get $219 x299 motherboard than outdated Z270 for $160.

    ...And as for heat...i think heat talk i have been reading lately is just BS.


    I agree that it's cool you have upgrade options when you buy an x299 motherboard. You can spend $350 on Kaby Lake X now then drop another $1000 in the future if you feel the need to buy Skylake X. It seems like Tomshardware didn't give credit to this upgrade path $1350 upgrade path where it's due.

    Some people might just buy Skylake X to begin with and save $350 on Kaby Lake X, but I ask "Why not both?"

    I think you hit the nail on the head on your x299 chipset point. The x270 chipset was obsolete when it launched with Kaby Lake 6 months ago. I'm glad Intel is giving a chance to rectify the situation by giving us access to the x299 chipset. So what if most of the motherboard is disabled because of the architectural differences between Kaby Lake X and Skylake X? What were you going to use those extra PCIe lanes for? Extra professional devices? Psh, whatever.

    Good point about the heat too. I'm tired of people using lines and graphs for stuff. It makes my head hurt. These nerds at Tomshardware could learn a thing or two from our president and just ignore that crap. The heat won't be a problem until you start Windows. That's why you use LINUX!

    Thanks for posting freak777power. We friends <3
    6
  • mossberg
    Anonymous said:
    This is awesome setup because you can buy x299 motherboard for $219 dollars already which gives you amazing room for later upgrade and this CPU can run 5.0Ghz easily producing very little heat. People at Toms Hardware completely missed the point. I'd rather get $219 x299 motherboard than outdated Z270 for $160.


    I would rather take that $60 and get a better graphics card. Why waste this kind of money on a 4c/8t system, when you can get a Ryzen 1700, with 8c/16t, for a similar cost? The R7's are plenty capable at gaming, and are great in workstation type apps. X299 is an overpriced waste of time. I think Linus had it right when he called it a knee jerk reaction.
    0
  • PaulAlcorn
    Anonymous said:
    Quote:
    The curve below shows clearly that waste heat isn't dissipated quickly enough. Just as we did in our AMD Ryzen and Intel Core i9 launch articles, we used a very thin copper plate to measure the heat spreader's temperatures as well.

    Why aren't there any numbers/divisions on the horizontal axis? Also, you say you did the same thing for the Ryzen reviews but I didn't see a similar graph in those articles (might just be blind though).


    We've done a LOT of Ryzen reviews, so this might not be the only one that included the test data.

    http://www.tomshardware.com/reviews/amd-ryzen-5-1600x-cpu-review,5014-8.html

    I'll circle back with Igor about the axis.
    1
  • PaulAlcorn
    Anonymous said:
    in the HPC graph, you have two 'Ryzen 7 1600x' s.....


    Which particular graph? I'm looking over them, but don't see it.
    0
  • PaulAlcorn
    Anonymous said:
    in the HPC graph, you have two 'Ryzen 7 1600x' s.....


    Which particular graph? I'm looking over them, but don't see it.
    0
  • PaulAlcorn
    Anonymous said:
    And as for heat...i think heat talk i have been reading lately is just BS.


    http://www.tomshardware.com/reviews/-intel-skylake-x-overclocking-thermal-issues,5117.html
    1
  • Anonymous
    I setup couple machines with x299 with 6 and 8 cores for other people and with 4.2Ghz on 8 Core and 4.5Ghz on 6 Core overclock nowhere to see heat problem. Granted we didn't run Prime but guess what, who plays Prime95 anyway? That unrealistic test will heat up anything you throw at. In other words in everything else i haven't seen 8 core going over 60C at all and idles between 25/30C and entire setup was in Thermaltake X31 with one of the AIO 240mm watercooling kits. I still say, this heat talk is just BS.
    -3
  • Anonymous
    Anonymous said:
    Quote:

    This is awesome setup because you can buy x299 motherboard for $219 dollars already which gives you amazing room for later upgrade and this CPU can run 5.0Ghz easily producing very little heat. People at Toms Hardware completely missed the point. I'd rather get $219 x299 motherboard than outdated Z270 for $160.

    ...And as for heat...i think heat talk i have been reading lately is just BS.


    I agree that it's cool you have upgrade options when you buy an x299 motherboard. You can spend $350 on Kaby Lake X now then drop another $1000 in the future if you feel the need to buy Skylake X. It seems like Tomshardware didn't give credit to this upgrade path $1350 upgrade path where it's due.

    Some people might just buy Skylake X to begin with and save $350 on Kaby Lake X, but I ask "Why not both?"

    I think you hit the nail on the head on your x299 chipset point. The x270 chipset was obsolete when it launched with Kaby Lake 6 months ago. I'm glad Intel is giving a chance to rectify the situation by giving us access to the x299 chipset. So what if most of the motherboard is disabled because of the architectural differences between Kaby Lake X and Skylake X? What were you going to use those extra PCIe lanes for? Extra professional devices? Psh, whatever.

    Good point about the heat too. I'm tired of people using lines and graphs for stuff. It makes my head hurt. These nerds at Tomshardware could learn a thing or two from our president and just ignore that crap. The heat won't be a problem until you start Windows. That's why you use LINUX!

    Thanks for posting freak777power. We friends <3


    I find your post rather pretty amusing. Extra PCIe lanes get disabled but that's because of number of PCIe quad core carries, nothing there to worry about. Again $219 x299 is way better deal than Z270 giving you hell of more options currently and in the future. I setup couple 6 and 8 core x299 machines and haven't seen any heat or throttling issues. Rule of thumb is don't trust anything you read these days and do your own research and then make conclusion.
    -2
  • TJ Hooker
    Anonymous said:
    Anonymous said:
    Quote:
    The curve below shows clearly that waste heat isn't dissipated quickly enough. Just as we did in our AMD Ryzen and Intel Core i9 launch articles, we used a very thin copper plate to measure the heat spreader's temperatures as well.

    Why aren't there any numbers/divisions on the horizontal axis? Also, you say you did the same thing for the Ryzen reviews but I didn't see a similar graph in those articles (might just be blind though).


    We've done a LOT of Ryzen reviews, so this might not be the only one that included the test data.

    http://www.tomshardware.com/reviews/amd-ryzen-5-1600x-cpu-review,5014-8.html

    I'll circle back with Igor about the axis.


    Thanks. If we get the horizontal axis for the graph, we could then look at the slopes of the core temp vs power for Ryzen/Skylake-X/Kaby Lake-X (all using a constant 20C waterblock) as a way to compare the effective thermal resistance of their respective TIM+heatspreader.
    0
  • tuvok
    Good review, now de-lid it and pair with 3600Mhz+ ram and stretch its legs.
    0